Finish wrapping the fabric on the ends of the header rail. Position the seam in the fabric on the end of the rail and about flush with the bottom surface of the rail. Wrap the fabric around the back of the rail, fasten in place and trim off any excess fabric. Follow up by stapling the rest of the large flap down on top, then trim off the excess fabric for the full length of the header rail. By now the header rail should be completely covered in fabric with nothing left hanging out except for the drop flap on the front of the windscreen.